Extruded rubber hose is manufactured by different processes. In one such process, extruded rubber hose is manufactured to maximum lengths dictated by the ability to vulcanize the hose. The length of the vulcanizing table determines the length of the hose. Similarly, other vulcanizing devices such as steam autoclaves and hot air ovens limit the length of the hose.
In the past extruded rubber hose was cooled upon exit from an extrusion die. As hose exits the extrusion die it is under the tension of haul off equipment. Unwanted diametrical reduction of the hose occurs due to tension of the haul off equipment. Upon exiting the cooling tank the hose cover is perforated about its circumference many times. The perforations are numerous and very close together.
After the hose cover is perforated as described it is removed from the production line and loaded into a container for transport to a vulcanizing table. Care must be taken in handling the hose because the rubber of the hose may be nicked, scratched or cut easily as it is very soft and pliable in its unvulcanized state. The length of the hose loaded in the containers is limited by the length of the sloped vulcanizing table. Sloping of the vulcanization table is necessary for steam condensate to drain.
When the hose reaches the vulcanizing table it is placed thereon and laid out lengthwise and coupled with fittings whereupon it is pressurized with steam for a period of time. Pressurization of the hose with steam increases the diameter of the elastomeric hose to the desired diameter and cures it. Perforations allow gases to escape from the hose cover during vulcanization.
After the hose is vulcanized it is removed from the vulcanization table and coated with latex to fill the holes. Unfilled holes can accelerate degradation of the woven fabric which acts as the superstructure (reinforcement) of the hose. Rubber hose is often used in corrosive environments where the warp and weft fibers of the woven jacket may degrade if they come in contact with certain chemical compounds.
Another process for manufacturing extruded rubber hose is set forth in U.S. Pat. No. 4,559,095 to Babbin at col. 5, line 21. Babbin indicates that an externally jacketed “tubular article” may be inflated during the vulcanization process to maintain the circular cross-sectional shape of the tubular article. Pressurization takes place while a length of the cut hose is inside the vulcanizing autoclave or oven. A thermoplastic external jacket is extruded about the rubber hose and protects the hose from scrapes, nicks, dents, grooves or the like before or during vulcanization. Conventional pressurizing methods or apparatus may be used during vulcanization. The external jacket is stripped away subsequent to the curing step. Table I of the '095 patent teaches autoclave curing of the rubber at 300° F. for 50 minutes with a 10–15 psi differential pressure. Example 4 teaches placing the hose in a microwave boost for 30 to 180 seconds followed by curing in a hot air oven for 30 to 40 minutes at about 307° F. The '095 patent does not teach continuous manufacture and vulcanization of elastomeric hose under pressure. Nor does the '095 patent teach endless manufacture and vulcanization of elastomeric hose under pressure.
Another process for manufacturing extruded rubber hose is set forth in U.S. Pat. No. 3,966,387 to Babbin et al. which discloses a helical extending vulcanizing chamber with entrance and exit sealing means. The hose assembly as it passes through the apparatus comprises a typical elastomeric hose structure and an internal, removable, flexible support mandrel typically made of solid rubber or plastic. Continuous vulcanization of elastomeric hose free of an outer pressure sheath or covering occurs by means of hot fluid. Hot fluid vulcanizes and transports the hose and contacts the exterior of the hose. See, FIG. 3 of the '387 patent.
Another process for manufacturing extruded rubber hose is set forth in U.S. Pat. No. 4,702,867 to Sejimo which discloses a “method for continuously vulcanizing rubber hose under normal pressure while preventing foaming of the unvulcanized rubber by covering the hose with a thin layer of resin.” See, col. 2, lines 5–8 of the '867 patent. The process is not continuous, however, but occurs in two steps. A first step of heating in a microwave vulcanizing tank to a temperature which causes partial vulcanization of the hose followed by placement of the hose in a heated vulcanizing tank until vulcanization of the hose is completed.